Reporting from Moscow and Los Angeles — — As Olga Digonskaya held the faded, long-lost documents, her body shaking with emotion, she was transported backward 70 years into Soviet-Russian history.

"I sat there speechless and my hands and legs were trembling," Digonskaya recently recalled of that gray December day in 2004.

Had she stumbled upon Joseph Stalin's secret diaries? Or perhaps a trove of his political enemies' trumped-up "confessions"?

Not quite. But in some ways, what the eminent musicologist had discovered speaks volumes about the hopes surrounding the early Soviet Union, the artistic flowering of that short-lived era, and the dark forces that soon would enshroud them both.

From an ordinary cardboard file, stashed away for decades in the Glinka State Central Museum of Musical Culture in Moscow, Digonskaya had unearthed a fragment of a long-lost opera, "Orango," by Russian composer Dmitri Shostakovich, an artist intimately, if reluctantly, bound up in the political skulduggery of his time.

The bizarre story of a grotesque, morally degenerate half-human, half-ape, "Orango" was commissioned by the Bolshoi Theater in 1932 and intended to commemorate the 15th anniversary of the October Revolution. Its restored, roughly 40-minute prologue, which is all that remains of the planned four-act work, will receive its world premiere Dec. 2, 3 and 4 at Walt Disney Concert Hall. Peter Sellars will direct the semi-staged production, and the virile young baritone, Eugene Brancoveanu, a performer noted for his superior acting and charisma, will sing the title role. Esa-Pekka Salonen will conduct the Los Angeles Philharmonic.

British composer Gerard McBurney, artistic programming advisor for the Chicago Symphony Orchestra, was hired by Irina Antonovna Shostakovich, the composer's third wife and widow, to orchestrate the score from surviving piano sketches.

In a phone interview last year, he described "Orango," which has a libretto by Alexei Tolstoy and Alexander Starchakov, as a brutal satire of the Western world, similar in its eclectic musicality and slashing comic tone to other Shostakovich works of the period, such as the ballet "The Bolt," the opera "Lady MacBeth of the Mtsensk District" and "Declared Dead," a.k.a. "Hypothetically Murdered," a 1931 vaudeville revue.

"The young Shostakovich, the rebel, the satirist, the hooligan, the comedian, I've found that side of him fascinating," McBurney said. "I'm not going to claim 'Orango' is going to change everything we know about Shostakovich, certainly not. But I think it's an important addition to what we know."

In response to email questions, Irina Shostakovich expressed satisfaction that the remains of "Orango," a work her husband never mentioned in her presence, finally would be performed. She is expected to attend the world premiere in Los Angeles.

"Another page from the creative life of Dmitry Dmitriyevich has opened up for me, and I decided that this unfinished composition can be interesting to all those who love Shostakovich's music," she wrote.

The opera's plot was inspired by the failed real-life experiments of a lunatic Russian geneticist, Ilya Ivanov, who tried to cross-breed humans and apes. The prologue sets up the tale of the rise and fall of Orango, a.k.a. "Jean Or," a human-ape hybrid who becomes a virulent anti-communist and newspaper baron through a combination of sleazy journalism, stock exchange swindles and ruthless blackmail, before his corrupted humanity causes him to revert back to his bestial nature. He is then put in a cage and displayed as a cautionary tale.

Much of Shostakovich's recently unearthed work apparently survived only by chance. A composer friend bribed Shostakovich's housemaid to regularly deliver the contents of Shostakovich's office waste bin to him, instead of taking it to the garbage. Some of those cast-offs eventually found their way into the Glinka.

For Digonskaya, who'd been working with Irina Shostakovich for many years to help maintain and catalog the composer's voluminous output, finding a dusty file stuffed with about 300 pages of musical sketches, pieces and scores all bearing the touch of a familiar hand was like opening "a treasure box," she said. The Glinka archive "contained a huge number of pieces and compositions which were completely unknown or could be traced quite indirectly," Digonskaya said.

But the real jewel was "Orango," the existence of which many scholars had doubted.

"When I barely touched the yellowish pages and looked at the manuscript, the faint blue letters and signs started dancing in my eyes and I almost lost my breath as I heard the music in my head," Digonskaya said. "Then I felt such a surge of energy as if I were a hound that hit the prey's scent."